The present invention relates to carbon blacks, compositions containing the carbon blacks, such as elastomeric or rubber compositions, methods of making the carbon blacks, as well as methods of using the carbon blacks.
Industrially manufactured carbon black is produced by pyrolysis of hydrocarbons at high temperatures under controlled process conditions. Under these conditions, trace levels of polyaromatic hydrocarbons, also known as PAHs, form on the carbon black surface.
Some PAHs have the potential to cause adverse health effects. Although the PAHs that are adhered to the carbon black are not readily available for human exposure, actions are being taken by both EU regulators and customers to reduce the concentration of PAHs in carbon black (See Borm P J, et. al., Formation of PAH-DNA adducts after in vivo and vitro exposure of rats and lung cells to different commercial carbon blacks, Toxicology and Applied Pharmacology, 2005 Jun. 1; 205(2): 157-167.). Recent examples include:                Promulgation of EU directive 2007/19/EC which harmonizes the rules for the plastic materials and articles intended to come in contact with food. The directive establishes a Benzo(a)pyrene content of 0.25 mg/kg in carbon black. Previous to this directive, no PAH limit existed for carbon black.        Promulgation of EU directive 2005/69/EC which regulates the content of PAHs in extenders oils used for the production of tires. This directive does not directly regulate the content of PAHs in carbon black; however, the EU has chosen to restrict the content of PAHs in extender oils and blends used to produce tires, in order to reduce the total annual emissions of PAHs, as required in the 1998 Protocol to the 1979 Convention on Long Range Transboundary Air Pollution on Persistent Organic Pollutants.        
The above listed examples demonstrate the growing trend towards lower PAH carbon blacks.
While there is a growing desire to have lower PAHs for carbon blacks, any reduction in PAH cannot compromise the desirable performance properties of carbon black in rubber and other applications. Thus, it is desirable to reduce PAH concentration in carbon black without sacrificing the properties achievable by the current carbon blacks.